Notes/Domino 8.5.2 Fix Pack 4 is a scheduled Fix Pack of low-risk, high-impact fixes to help customers safely avoid known issues. IBM strongly recommends that customers running Notes/Domino 8.5.2.x this latest Fix Pack since it addresses a small percentage of defects that impact the broadest set of customers. Fix Packs are released periodically between Maintenance Releases to provide a greater level of stability for customer environments. They go through the same level of fix, regression and interoperability testing that occurs with Maintenance Releases. Fix Packs are always cumulative and contain all of the fixes from previous ones.